Portion of a cabinet shelf



FIG. 1 is a top perspective view of a portion of a cabinet shelf;

FIG. 2 is a right side elevation view thereof, with a left side elevation view being a mirror image thereof; and,

FIG. 3 is a front elevation view thereof.

The dashed broken lines in FIGS. 1, 2 and 3 represent environmental subject matter and form no part of the claimed design. 

The ornamental design for a portion of a cabinet shelf, as shown and described. 